The objective of these studies is to improve understanding of the role that indoor allergens play in asthma and to establish effective regimes for treating the disease by reducing exposure to allergens in homes. Asthma affects at least 8 million people in N. America, and the disease appears to be increasing both in prevalence and severity. Case control studies on emergency room patients suggest that greater or equal to 40% of adult asthma and as much as 75% of asthma among children is related to sensitization to indoor allergens. These studies utilize rapid sensitive monoclonal antibody based immunoassays for allergens derived from dust mites of the genus Dermatophagoides, the cat Felis domesticus and cockroaches, eg. Blatella germanica. In order to understand the relevance of exposure in childhood, tbe prevalence of asthma among chfldren age 12-14 will be assessed and related to the allergen levels in houses in different climatic areas. These studies will be designed to answer whether exposure in houses influences the sensitization of children and also whether high levels of exposure can increase the prevalence of asthma. The results should also allow a reevaluation of the proposed threshold levels that are associated with increased risk of sensitization to mite or cat allergens and with the development of asthma. The present experiments will also focus on techniques for reducing exposure to dust mite and cat allergens. In particular, the effects of both physical measures (e.g. covering mattresses, hot washing bedding, removing carpets) and chemical measures (e.g. acaricides or denaturing agents applied to carpets and sofas) on airborne dust mite allergen will be investigated. Similarly, detailed measures for controlling exposure to cat allergens will be studied (e.g. air filtration, removing carpets and washing the cat). Finally, controlled trials of allergen avoidance will be carried out on children admitted to hospital with asthma, patients presenting to clinics with asthma, and also on mite allergic patients with atopic dermatitis. The long term objective is to develop effective and realistic methods for reducing exposure to allergens and to answer whether allergen avoidance should be a first line form of treatment for these patients.